Hot-air blast



.(No Model.) W. 0. MILLS.

HOT AIR BLAST. N0. 396 ,9 17. Patented Jan. 29, 1889.

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UNITED STATES PATENT OEEIcE.

\VILLIAMI). MILLS, OF SAN FRANCISCO, CALIFORNIA.

HOT-A| R BLAST.

SPECIFICATION forming part of Letters Patent No. 396,947, dated January29, 1889.

Application filed June 19, 1888. Serial No. 277,604. (No model.)

To all whom it may concern:

Be it known that I, IVILLIAA'I O. MILLS, of the city and county of SanFrancisco, State of California, have invented certain new and usefulImprovements in Air-Heating Apparatus for the Furnaces ofSteam-I-ioilers; and I do hereby declare that the following is a full,clear, and exact description of the same.

This invention relates to means for conducting hot air from a casingsurrounding the smoke-stack of a locomotive or engine to the ash-box orbeneath the grate by the aid of a jet of steam; and the improvementswill be fully understood from the following descripti on and claims whentaken in connection with the annexed drawings, in which Figure 1 is afront view of a furnace, showing my improvements applied. I ig. 2 is aside elevation, partly in section, of the smokestack and easingsurroiniuling the same, with a portion of the pipe which leads therefromto the ash-pit of the furnace; and Fig. 3 is a perspective view of thejacket or casing removed, with the hot-air conneeting-pipe dctached.

Referring by letter to the said drawings, A indicates a furnace, whichmay be that of any ordinary or approved construct-ion, hav- Thesmokc-staclgwl1ich p r( )p erlyl cads from th e :t'urnace, is composed.of tubes l for cz'irrying off the smoke and particles of combustion, andarranged at intervals so as to form between and around them air-passagesI). Surrounding these smoke-tubes is a tubularcasing, which is providedin its body with apertures I) for the introduction of cold. air, andthis casing surrounds the said tubes l) for a sufficient portion oftheir length. It should be observed that this perforated jacket orcasing may be applied to any tubular smokestack; or, in fact, any smole-stack-such as at present in use-without altering the construction ofthe latter in any maimer whatever; and to this feature of construction Iattach considerable importance.

In applying the jacket or tubular casing it is simply necessary to slipthe same down upon the stack to the base thereof, the upper portion ofthe said casing being contracted, as shown at II, will approximatelyengage the outer surface of the stack and thereby retard the free egressof the radiated heat.

' E indicates a pipe, which leads from a suitable point at the base ofthe casin g surrounding the smoke-tubes to the ash-pit beneath thefirebox, as shown at G, so that the cold air which enters the casingthrough the perforations I) therein and has become heated by contactwith the smoke-tubes may be con ducted to the ash-pit and theredischarged to feed the tire and promote combustion.

F indicates a steam-pipe, which enters pipe E at its point of connectionwith the ashchainber. It will thus be seen that by the injection of ajet of steam into this pipe E where it connects with the ash-chamber theair, it is heated in the smoke-stack, will be drawn down through thepipe E and forced into the ash-chamber beneath the fire-grate. Thisoperation will take place when the doors to the ash-chz'unber have beenclosed and cold air thereby excluded from thc'tirc-chamber.

I am aware that it is not new to feed heated air to a fire in a furnacewhile excluding cold air therefrom, and that air, superheated steam, andhot gases arising from the combustion-chamber have been forced into thefuel to aid in its combustion.

By this invention it will be seen that the improvements may be appliedto any ordinary ecomotive-engine without altering its construction inany manner whatever, it being simply necessary to slip the perforatedjacket 0 over the smokestaek and communicate the same with theash-chamber of the furnace by means of the pipe E.

Having described my invention, what I claim is The coml'iination, with afurnace, of the smoke-stack composed of tubes 1- for the passage ofsmoke and particles of combustion, the casing O, surrounding the saidtubes and having perforations Z) entirely around the same at its upperportion for the inlet of cold air, which passes around the smoketubes,and also having its upper end contraoted to approximately bear againstthe thrown to draw the heated air in the snookeouter surface of thestack, the pipe E, leadstack or its easing into the -ashpit beneath ingfrom the lower portion of the said casing the fire, substantially asspecified.

below the perforations to the ash-pit of the WM. 0. MILLS. furnace, andthe steam-pipe F, entering the \VHJHGSSQSI said pipe E at its point ofconnection with \VM. LUTHER,

the ash-pit, whereby a jet of steam may be JOHN MILLS.

